The invention broadly relates to ore grinding machines and is specifically directed to an improved segmented liner assembly and the individual segments for the discharged end of an ore grinding machine.
Ore grinding machines are commonly used as one step in the process of reducing the size of ore in commercial mining operations. One type of ore grinding machine consists of a large cylindrical drum mounted on bearings for rotation about a substantially horizontal axis and driven by a powerful motor through conventional reduction gearing. The cylindrical drum may be of differing diameters depending on the needs of the operation and may reach diameters of 40 feet.
The ends of the drum are substantially closed but respectively define an axial inlet opening and an axial discharge opening. The ore which is to be ground or comminuted is continuously fed into the mill at the inlet end with the product of reduced size continuously emerging from the discharge end.
It is conventional to line the cylindrical drum with liner segments of different configuration and different metallurgical hardness to enable the ore to be comminuted as efficiently as possible while minimizing the wear rate of the individual segments. Commercial mining operations typically operate 24 hours a day, and down time to remove a worn set of liner segments and replace them with new segments is a time consuming process.
The discharge end of the cylindrical drum is typically conical in shape and includes one or more sets of end liner segments that are arranged in a radial pattern relative to the axial discharge opening. In larger mills there may be two or three sets of discharge end segment assemblies which are arranged concentrically relative to the axial discharge opening, with the segments of one assembly aligned radially with the segments of a contiguous assembly.
It is also common to cast the individual segments of the discharge end in a hollow manner so that each defines a large radial trough. With the radial channels of contiguous concentric assemblies aligned radially, comminuted ore may enter the radially extending channels of the discharge end liner assembly and be centrifugally forced radially inward toward and out of the discharge outlet.
As suggested above, the replacement of liner assemblies in the cylindrical drum of an ore grinding machine is a difficult and time consuming task. Each of the individual segments may weight several thousand pounds, and it must be placed in its proper position for mounting. The mounting of liner segments is typically accomplished a plurality of bolts for each segment that extend trough bolt holes in the segment itself and aligned bolt holes in the cylindrical drum. Proper alignment must occur before the bolts can be inserted and fastened.
The problem is even more difficult with regard to the liner segments in the discharge end of the cylindrical drum, particularly where two or three concentric assemblies are mounted. Conventionally, the outermost assembly is installed first followed by the next concentric assembly the individual segments of which may rest on the now installed first assembly. However, it is quite difficult to properly locate the individual segments of the outermost concentric assembly, which is the first step in the process.
Another problem arises with the liner segments in the discharge end of the cylindrical drum. Conventionally, the comminuted ore fragments are allowed to be discharged only after they have been reduced to a predetermined size. This is accomplished with a large grate that forms part of the discharge end of the mill. The grate has openings of a predetermined size, and the ore can be discharged only if it is small enough to pass through these grate openings.
The problem arises from the fact that clearance is designed between the segment mounting bolts and the bolt holes in the liner segment and/or the aligned bolt holes in the cylindrical drum. Clearance is also necessarily designed between the sides of each segment and its adjacent segments. This bolt hole and side-to-side clearance facilitates installation of the liner segments due to their extreme size and weight. In other words, without the clearance it would be extremely difficult to precisely place the segment to gain alignment of the bolt holes while at the same time squeezing the segment end relative to its adjacent segments.
While these clearances facilitate installation, they also create a problem because the segments on the discharge end tend to migrate radially outward due to centrifugal forces created as the drum rotates. As a result, all of the gaps that normally exist between adjacent segments accumulate in a single gap that may itself be larger than the grate opening that sizes the ore fragments. As a consequence, oversized fragments may be discharged from the mill.
This invention is directed to a unique locating device for the discharge and liner assembly, and particularly for the outermost concentric liner assembly of the ore grinding machine. The locating device in the preferred embodiment comprises a pin or boss that is cast on the backside of each liner segment (i.e., the side which faces and mates with the discharge end of the cylindrical drum), and which is disposed to fit into an existing bolt hole in the cylindrical drum. This advantageously makes use of the existing bolt holes in the cylindrical drum without requiring modification.
During installation, the individual segments having locator pins are placed with the locator pin projecting into the locator opening, which effectively aligns all of the bolt holes of a segment with the bolt holes in the cylindrical drum. This saves considerable time and effort in installing these end segments.
Once the outermost concentric liner assembly is installed on the discharge end of the cylindrical drum, the individual segments of the contiguous liner assembly can be mounted. Locator pins may also be used for this purpose, although it is conventional for the contiguous segment to be configured in such a manner that it mates with and becomes radially aligned with the previously mounted segment, thus establishing alignment of the radial troughs through which the comminuted ore passes. If a third concentric assembly is used, it is similarly constructed and mounted in the same manner.
The use of this simple locating device makes the installation procedure much easier for the workmen installing the liner assembly, saving significant time in the installation procedure and thus reducing the down time of the mill. The locating device also serves to retain the liner segments in the initial installation position, thus preventing outward migration due to centrifugal force. This in turn avoids oversize fragments being discharged from the mill.
The specific structure and features of the invention will be more fully appreciated from the specification and drawings.